Filters in many technical domains (automobile industry, household appliances, computer hardware, etc.), parts, especially plastic injection molded parts must be very precisely positioned relative to each other before their assembly using screws or pins for assembly.
Such prior positioning is for example often necessary in the automobile industry, especially for mounting of closure plates, air intake collectors, cylinder head covers or other parts under the hood of automobiles.
In particular with air intake manifolds or other under the hood components, an improper alignment of the air ducts at the connecting flange on the engine can result in reduced air flow, increased pressure drop as well as possible improper sealing and seal leakage at the connection between the air intake manifold and the cylinder head of the internal combustion engine.
Conventionally such positioning is done by means of centering posts or guide pins which are molded on one of the parts to be assembled and placed into corresponding centering holes, either through holes or not, formed in the other part. The assembly of the two parts is then done by means of screws or pins placed into the associated holes.
In the common case of parts made from creep sensitive material, these centering holes are conventionally equipped with spacers which serve the purpose of limiting compression in order to reduce the deformation of the part by creep under the action of temperature and guarantee the firm clamping of the assembled parts over time.
In the prior art, spacer elements or compression limiters are usually pressed into mounting holes in the creep sensitive material part after the part is manufactured or molded.
Such a positioning system has the disadvantage of creating fragile zones or weak points in the parts to be assembled (posts or pins) and also require the addition of supplemental elements such as centering holes which thereby increase the complexity and cost of the parts.
To remedy this disadvantage, it has already been proposed to replace the centering system using posts with a system using positioning screws placed into corresponding holes of each of the parts to be positioned and assembled. The implementation of such screws acting as centering posts has not however turned out to be satisfactory for use to the extent where they do not make it possible to obtain a sufficiently precise positioning.
Using attachment screws engaging with oblong compression limiters has also been proposed, but that leads to significant extra costs while also increasing the implementation complexity.
The use of oblong or oval compression limiters with a larger diameter and a traversing smaller diameter to the axis of the screw are seen as complex in production of creep sensitive parts as such compression limiters are difficult to handle when pressing them into the preformed receiving holes in the part. Due to tolerance variations in the compression limiters and parts, the danger exists that the compression limiters may separate from the part during transport or handling. Additional problems arise as the process of pressing the compression limiters into the receiving holes of the part may generate splinters or otherwise damage the receiving hole, resulting in a damaged part or a less than desired press fit.
Additional problems are from the use of both oblong and cylindrical compression limiters in the same parts these differing compression limiter geometries can be intermixed and thereby inserted into a receiving hole having geometry different from the compression limiter being inserted, resulting in damage to the part or a manufacturing defect.